The art of printing images with micro-fluid technology is relatively well-known. In thermal inkjet printing technology, thermal inkjet printers apply ink to a print medium by ejecting small droplets of ink from an array of nozzles located in a printhead. An array of thin-film resistors on an integrated circuit on the printhead selectively generates heat as current is passed through the resistors. The heat causes ink contained within an ink reservoir adjacent to the resistors to boil and be ejected from the array of nozzles associated with the resistor array. A printer controller determines which resistors will be “fired” and the proper firing sequence thus controlling the ejection of ink through the printhead so that the desired pattern of dots is printed on the medium to form an image.
For the ink supply, ink in thermal inkjet printers using an on-carrier ink supply system may be contained in printhead cartridges which include integrated ink reservoirs. The printhead cartridges are mounted on the carriage which moves the printhead cartridges across the print medium. The integrated ink reservoirs often contain less ink than the printhead is capable of ejecting over its life. Several methods now exist for supplying additional ink to the printhead after the initial supply in the integrated reservoir has been depleted. Most of these methods involve continuous or intermittent siphoning or pumping of ink from a remote ink source to the print cartridge.
The remote ink source is typically housed in a replacement ink container which is “off-carrier,” meaning it is not mounted on the carriage which moves the printhead cartridge across the print medium. In an off-carrier ink supply system, the ink usually travels from the remote ink container to the printhead through flexible conduits extending from the replacement ink container to the printhead cartridge. Before actual use of the inkjet printer, the flexible conduits are filled with air which must be removed from the system prior to usage of the inkjet printer. In conventional inkjet printers, the air is removed by priming wherein the air is removed from the flexible conduits through the nozzle holes by a suction force and for a predetermined period. During priming, it is unavoidable that a certain volume of ink is sucked together with the air. The ink sucked during priming is discarded as waste ink. After initial use of the inkjet printer, air accumulates in the flexible conduits when the inkjet printer is idle or not in use for an extended period of time. The accumulated air is removed by purging. Priming and purging refer to the same process, the only significant difference being the time the process is employed. Priming is performed during initial use of a printhead while purging is employed during regular operation of the printhead. Both priming and purging remove air from the flexible conduits and discard a certain volume of ink as waste ink.
Accordingly, a need exists in the art for a system of removing air from ink supply line without wasting ink.